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Lots of questions on grinding/sanding a blade


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I am very close to finishing my third knife. I am very pleased with how it is turning out. Currently using my 2x72 grinder I am grinding, shaping, and finally sanding to about 320 to 400 grit. All of my sanding marks will be situated from spine to edge.

 

Then I am handing sanding (which I hate) up to 600-1000 grit. This situates my sanding marks from tip to end. While this looks good, I have some questions.

 

I see so many beautiful knives on here with very distinct grinds and sharp transitions and bevels. While I am still learning to control my grid, when I switch to hand sanding, my bevels and transitions become a lot less distinct.

 

How many of you only sand with grinder? Is it okay to only have sanding grain run from spine to edge? If not, how do you keep the bevels and edges crisp?

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The way you keep things crisp with hand sanding is to use a single sheet thickness on a rigid backing. I wrap mine onto a bar of 1/4" x 1" steel, but hard wood, corian, micarta, and so on work well also. Use the best quality wet-or-dry paper you can find and use it wet.

 

Jim Batson recommends getting the cheap spray glue from Walmart since it doesn't stick very well and you can just peel off a worn out strip of paper.

 

There are guys who do it all on the grinder, but they use a huge number of belts of ever-finer grit, often followed by a cork belt with stropping compound. My hands aren't steady enough for that, so I only grind up to around 220 and do it all by hand from there. In fact, I'll often drawfile after rough grinding just to get things truly flat.

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When you're on the lower grits, go at an angle to the blade, changing directions every sheet of paper or so to make sure you've got all the scratches out. When you get to your target finishing grit, lengthwise strokes without scrubbing leave a satin finish. If you scrub back and forth you'll leave little swirlmarks that are a pain to remove.

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Visually, I think it looks better is the scratches run the long way on a blade. I machine grind up to about 220. I actually use Gator belts as my last 3 grits, so I go 36, 60, 100, then switch to the Gators. The last Gator is about a 220 grit, but I think its finer than a standard grit. All of that runs from spine to edge. Then I start the hand work. I use the black Silicon automotive papers. Using a backer I start sanding down the length of the blade. Depending on how well I got my scratches out in the machine sanding, getting a clean 220 surface can take a few minutes to an hour a side for a big blade. Once I have established that clean 220 surface, it takes just a few minutes a side to get to 1200, which is where I stop. Usually I stop at 320 and start fitting the furniture and the handle, then I can go back and take out any marks that the fit up causes, up to 1200.

 

I think the blades with the sanding marks going spine to edge look like factory knives. Look carefully at some of the production knives, I won't mention their name, but the "Chuck" knives have that "deeply scratched and highly polished" look. I don't think it looks good.

 

If I'm making a blade with no plunge cut, then I can grind lengthwise and that saves me a bunch of time setting up my 220 hand surface.

 

Geoff

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Just a quick note, but I bought a couple rolls of that adhesive backed Norton A/O paper that Don F. was using in Arctic Fire 2012, and I'm sold on that stuff.

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I've seen my mentor keep his spray a little WD-40 on the blade to keep it wet. I have to find some finer-grit paper before I can really speak with authority on it, though.

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Parrafin/kerosene is great and cheaper than wd40 If you sand from handle to tip you can keep the angle square from spine to tip you will end up with a 'rocking' motion, taking away definition...

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For sanding lube anything that keeps the blade wet will work. Water, oil, windex, all work fine. My current favorite is 5w-20 fully synthetic motor oil (new, of course!). It keeps a good slurry going, it's light enough to cut well, and it seems to help with swirl marks.

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I will have to look into this.

 

Thanks

 

Is this what you have?

 

http://www.onlineindustrialsupply.com/noada22x25ya.html

 

The stuff I have looks identical to these:

 

http://www.onlineindustrialsupply.com/nonoada22x25.html

 

I'll double check for an number.

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